Numerous devices are known that include a capacitive member for detecting or controlling the distance between two portions of the device that are movable relative to each other. In particular, it is known that capacitive members are used for detecting and controlling deformation of a mechanical resonator in a vibrating gyro, in particular an axisymmetric vibrating gyro. When such devices are used in free gyro mode, they present the advantage of having a scale factor (Bryan's factor) of very great stability.
In free gyro mode, the vibration is free and its plane turns about the axis of the resonator as a function of the movements of the carrier. To benefit from the advantages of this mode, it is essential to know accurately the position of the vibration relative to the housing of the apparatus in order to apply control signals that enable the vibration movement to be sustained. Any error in measuring the position of the vibration creates an error in the direction of the applied force and thus generates parasitic drift of the gyro.
Numerous attempts have been made to correct or take account of errors that occur in accelerometer measurements. Thus, documents US-A-2003/006783 and U.S. Pat. No. 6,035,694 seek to attenuate measurement error caused by stray capacitances that are substantially constant. Document U.S. Pat. No. 6,035,694 describes a similar solution.